I would say it'd be safer to wait until October, after your holiday. You can fill out and save the application in advance and then submit when you get back to the UK.
Applying on August 14th could be risky, as you can't guarantee that you'll get the visa in time, as it can take a couple of weeks or more to get a biometrics appointment, and then after the appointment, it can take up to 10 days to receive the new BRP... and you can't travel while you have an application pending (leaving the UK after applying but before getting the visa will invalidate the application).
I would get everything prepared before you go away (you can start the application and just keep saving it until you are ready to submit), and then apply as soon as you get home.